Australasian Science: Australia's authority on science since 1938

Carbon Storage Passes the Test

By Stephen Luntz

CO2 successfully contained underground in south-western Victoria.

For the first time, detailed monitoring has confirmed the success of carbon dioxide storage in an underground reservoir. The findings, reported in the Proceedings of the National Academy of Sciences, mark an essential step towards large-scale sequestration of power station emissions, although the work sheds no light on the economic viability of such programs.

Carbon dioxide has been injected into oil fields for some time, partly to store the greenhouse gas and partly as a way of forcing the oil to the surface. However, lead author Dr Charles Jenkins of the Cooperative Research Centre for Greenhouse Gas Technologies says that these projects, usually taking place in offshore oil fields, have not conducted the measurements required to confirm that the CO2 is staying underground.

Jenkins was part of a team that injected 65,000 tonnes of CO2 into a depleted natural gas reservoir 1.5 km under the Otway Basin in south-western Victoria.

“The work has been a major scientific and logistical exercise covering risk assessment, monitoring and verification, reservoir modelling, regulation and community relations, and has produced a huge amount of scientific and practical information on CO2 storage and monitoring,” Jenkins says.

A variety of monitoring methods confirmed that very little of the carbon dioxide has escaped, and measurements of the rate at which the gas dispersed through rock, sand and gravel beds deep under the surface have been incorporated into models for varying geologies.

Jenkins says the site was chosen because of the proximity of the reservoir to another geological structure containing carbon dioxide with a small amount of methane. Since the gas was transferred from one underground location to another, no emissions were prevented, but the work is a stepping-stone to the injection of gases captured from power stations or other large-scale sources.

The choice of location also enabled the team to conduct pre-monitoring of the site rather than having to move to the timetable of an industrial project.

The area is not very seismically active but Jenkins doubts even a major earthquake would cause a significant release, noting that the gas is captured in “minute pores in the rock” rather than a large empty basin. “If there was a fault that ran through it the CO2 would have to migrate to that crack to escape. It’s almost impossible to imagine,” he says.